1. Links from relevant sites
This is the most important quality parameter to measure the relevance of inbound link. However, this parameter has always been mistaken by most of the people.
For instance, link of a weight loss site on the website about travel. These are two different domains and are not relevant to each other.
Weight Loss visitor will be more intended to know about tips to lose weight, exercise and diets. Thus, it is quite obvious that they will never click your link about travel.
Tip: Focus on link worthiness and forget about link volume.
(ABCtravel.com links will get benefit of link if it comes from traveladviceXYZ.com)
2. Links from high PR website
Links from High PR are always recommended, but a High PR web page does not mean that it is the best page to get a link from. Page Rank of a webpage is shared equally among all links on that page and a web page with a high PR and many links could potentially pass only a fraction of PR in comparison to a lower PR page with small or almost no links on it.
Tip: Determining the actual value of a link is important to know, to get the maximum return from each and every link.
3. Sustainability of link
Link attainment or links preservation depends on webmasters relationship. Thus it is difficult to say that link will or will not stay longer. Online relationship plays an important role here. If the SEO person/webmaster has a good relationship with the other webmaster then only he/she can guarantee link sustainability for larger period of time.
With link sustainability, do keep in mind about the quality of linking page.
4. Price of link building
Cheap price not always mean cheap service. It just means relatively cheap. The first step here should be to measure your link value (according to the quality parameters) and then take the decision that you are paying right price for links or not.
Tip: Analyze the ROI of your each link so that you can get real value of your money.
5. Speed of Getting Inbound links
The speed at which the links are developed depends upon the domain competitiveness. Hence explore the domain, and then calculate the effort and time required for a specific Link Building campaign.
Tip: Develop link in a manner that it would look natural in respect to your domain.
Always remember, logic is of utmost importance here and your common sense can guide you to do the best. These are some tips which can help you while you are trying to build some links.